Everything You Need to Know About GMT Watches


Ideally suited for travel and keeping track of time in multiple locations, are widely considered to be one of the most practical types of timepieces, and they can be found in a variety of different shapes and styles. While they were originally designed for professional pilots, GMT watches are now worn by countless individuals all over the world who appreciate them for their functional versatility.

For anyone who is interested in learning more about this highly popular category of travel-ready timepieces, below we are breaking down a complete overview of everything that you need to know about GMT watches.

What Is a GMT Watch?

A GMT watch is a specialized type of timepiece that is capable of simultaneously displaying two or more timezones, with at least one of them being presented in a 24-hour format. This 24-hour time serves as a reference point, and by knowing the number of hours offset from the reference time zone, GMT watches are able to calculate any other time zone accordingly.

Different Types of GMT Watches

While there are several different types of GMT watches, the most common style features four centrally-mounted hands, with one of them being a 12-hour hand, and another being a 24-hour hand. The two hour hands can either be linked or independently adjustable, and among those that allow for independent adjustment, some permit the 12-hour hand to be set independently from the time, while others function the complete opposite and enable independent adjustment of the 24-hour hand.

True GMT vs. Office GMT Watches

One of the distinctions between different types of GMT watches is the concept of true GMT vs. office GMT models. Although both variations are GMT watches, the “true GMT” name typically refers to timepieces where the 12-hour hand can be adjusted independently, while the “office GMT” moniker describes those with an independently adjustable 24-hour hand.

Neither approach to the GMT watch is categorically superior to the other, and each one has its own strengths and weaknesses. True GMT watches are ideal for frequent travelers who often need to reset their watches when changing time zones. Meanwhile, office GMT watches are perfect for those who consistently need a secondary timezone display but are not actually changing their geographic location themselves.

With that in mind, the mechanics required for true GMT watches are more complex than those needed for office GMT models, and many of the best true GMT watches cost a minimum of several thousand dollars. Affordable true GMT watch options are few and far between, and this is because mechanical GMT movements are inherently more complex than their traditional three-handed siblings. Since automatic GMT watch options can often be expensive, GMT watch quartz movements are generally the go-to options for many affordable GMT watch models.

GMT Dive Watch

While the very first GMT watches were made for pilots, dive watches with GMT complications are now incredibly popular. Offering ample water resistance with the ability to keep track of time in multiple different locations, a diver GMT watch is the ideal go-anywhere timepiece that can venture anywhere you can, regardless of whether that is the top of a mountain or the bottom of the ocean.

How Does a GMT Watch Work?

Different styles of GMT watches will function slightly differently but among the traditional four-handed variety, most will work in a relatively similar manner. Just like a normal watch, the time is displayed by three of the four centrally-mounted hands, with the fourth hand being the 24-hour hand, which is used to display a secondary timezone, and this can be indicated against a corresponding 24-hour scale located on either the dial or the bezel of the watch.

How to Read a GMT Watch

The standard 12-hour hand makes two rotations of the dial each day and permits the local time to be read against the normal hour markers. However, the 24-hour hand only makes one full rotation each day, and since it presents the time in a 24-hour format, there is no possibility of mixing up AM and PM hours in your secondary timezone. Additionally, should your GMT watch have a rotating 24-hour bezel, turning it to correspond with the number of hours either ahead or behind of your current time will allow you to access a third time zone by reading the 24-hour hand’s position against the bezel’s scale.

How to Use a GMT Watch

One of the most practical ways of using a GMT watch is to set its 24-hour hand to GMT/UTC and have its 12-hour hand display your current time zone. This will allow you to read local time like normal, but it offers maximum flexibility when it comes to referencing other timezones.

In many instances, time zones are listed as their offset from GMT. For example, you might see Pacific Standard Time written as GMT-8 or Swiss time as GMT+2. By keeping the 24-hour hand on your watch set to GMT/UTC, you can rotate its bezel to correspond with the number of hours either backwards or forwards from GMT to easily tell the time anywhere else in the world.

The Most Famous GMT Watches

One of the first known instances of a purpose-built GMT watch was the Glycine Airman, which debuted in 1953 and featured a 24-hour display (where the hour hand makes one full rotation around the dial each day) paired with a rotating bidirectional bezel marked with a 24-hour scale, which allowed pilots to quickly access a second time zone. With that in mind, within a couple years of the Airman’s debut, the most famous GMT watch of all time also made its first appearance: the Rolex GMT-Master. Based around the now-standard GMT watch design with one 12-hour hand and one 24-hour hand, the GMT-Master is arguably the most legendary GMT watch of all time, and it forever set the standard for multi-time zone travel watches.

Where to Buy GMT Watches

Whether it’s used for travel or simply to keep track of the time in a different city for frequent business calls, a secondary timezone display is easily one of the most practical features that a wristwatch can have. Therefore, GMT watches have become incredibly popular among today’s collectors, but it is first important to figure out what type of GMT watch is best for you

The Best GMT Watches

The best GMT watch for one person might not be the best for another. For example, the commercial airplane pilot who spends every day crossing multiple time zones is almost certainly going to want to opt for a true GMT watch. On the other hand, a person who occasionally travels but spends most of their days communicating with people in different countries is guaranteed to find an office GMT watch more useful.

Additionally, beyond what type of GMT watch is better suited to your individual lifestyle, the aesthetic of the watch and any additional features it might offer can also be important factors. Someone who spends most of their days wearing a suit inside office buildings might want a GMT dress watch, while a person who frequently travels around the world exploring the outdoors might prefer a diver GMT watch due to its increased durability and water resistance.

The Formex Reef GMT Automatic Chronometer 300M

When it comes to Formex GMT watches, our flagship multi-timezone model is the Reef GMT Automatic Chronometer 300M. Expanding upon our popular Reef dive watch, the Formex Reef GMT features the same interchangeable bezel and bracelet systems, along with the same 300-meter depth rating, but it adds a sapphire display caseback and the ability to display three different time zones.

Powered by the Swiss-Made Sellita SW330-2 automatic movement, the Formex Reef GMT offers COSC chronometer-certified performance and a power reserve of approximately 56 hours. Additionally, its 24-hour hand can be independently adjusted and since the dial itself includes its own 24-hour scale, the rotating bezel on the Reef GMT can be used for quick access to a third time zone.

As a rugged yet refined timepiece built for a life adventure, the Formex Reef GMT is available with the option of a variety of different straps and bracelets to suit your individual lifestyle. Options include rubber, leather, and nylon, plus two different metal bracelets, and all of the clasps feature fine-adjustment systems, allowing you to get the perfect size for your wrist, regardless of whether you’re going out to dinner or going diving deep below the surface of the ocean.